The present invention relates to a thrust reverser for a turbojet engine, more particularly such a thrust reverser having vanes to control the direction of the gases emanating from the thrust reverser.
Turbojet engines are well-known in the art and may comprise a turbojet engine drivingly connected to a turbofan, usually mounted on the front of the turbojet engine. A turbofan housing, radically displaced from, but generally concentric with the turbojet engine housing, defines a cold flow air duct for air driven by the turbofan. In turbofan engines having a relatively high bypass ratio, thrust reversers are typically provided on the turbofan housing so as to redirect the air passing through the cold flow air duct during landing of the aircraft in order to provide a reverse thrust.
The housing for the turbojet engine has a hot gas flow duct for the hot gases emanating from the turbines of the turbojet engine. Thrust reversers may be associated with the hot gas flow duct to redirect the hot gas flow to provide a thrust reversing effect.
Thrust reversers may assume many different configurations, but a typical thrust reverser is illustrated in FIG. 1. The thrust reverser comprises a stationary, upstream portion 1 which forms a part of the engine housing, a movable portion 2 which may redirect the air or the hot gas flow and a stationary, downstream collar 3 which also forms a portion of the engine housing. The stationary upstream portion 1 typically comprises an exterior panel 4 which defines a portion of the exterior surface of the housing, an internal panel 5 which defines a boundary of the gas flow duct and a frame 6 which interconnects panels 4 and 5. The frame 6 also provides support for the actuator 7a which controls the movement of the movable portion 2 which, in this instance, comprises one or more movable thrust reversing doors 7. The number of such doors may vary depending upon the application of the engine to a particular type aircraft and typically may comprise 2, 3 or 4 such doors. The doors may be located around the circumference of the engine housing and, when in their deployed or thrust reversing positions, redirect the gas passing through the gas flow duct to provide a thrust reversing force. When in the closed, or forward thrust position, as illustrated in FIG. 1, the exterior panel 9 of the thrust reversing door 7 is flush with the outer surface of exterior panel 4 and the exterior surface of downstream collar 3 so as to provide a smooth aerodynamic surface for the air passing over the exterior of the housing, illustrated by arrow 10.
FIG. 2 illustrates an engine housing with a plurality of known thrust reversing doors 7 in their closed or forward thrust positions. When deployed to their open or reverse thrust positions, the forward, or upstream, edges are displaced radially outwardly from the generally annular engine housing. As is well-known in the art, rear, or downstream, portions of the thrust reverser doors 7 extend inwardly into the gas flow duct so as to redirect at least a portion of the gas outwardly through the opening in the engine housing in a forward direction. Each thrust reverser door 7 is operatively associated with a hydraulic jack or actuator 7a, which typically comprises a cylinder having an extendable and retractable piston rod attached to the thrust reverser door 7.
The terms "upstream" and "downstream" are defined in relation to the direction of air or gas circulation in the forward thrust mode, e.g., from the front of the engine towards the rear of the engine (left to right in FIG. 1). The air or gas passing through the gas flow duct, illustrated at 15 in FIG. 1, passes over the surface of internal panel 5 and over a deflector 8. Each thrust reverser door 7 has an interior door panel 11 which is connected to the exterior door panel 9 via brace 12 and a door gas deflector 13. Door gas deflector 13 extends radially inwardly past the surface of interior door panel 11 such that, when the thrust reverser door 7 is in its thrust reversing position, door gas deflector 13 will impart a more forward direction to the gases passing through the opening in the engine housing. When in its closed, forward thrust position, the thrust reverser door 7 forms part of the boundaries of cavity 16, which is bounded by the interior door panel 11, the deflector 8, the door air deflector 13 and line 14, which represents the ideal, theoretical surface interconnecting the internal panel 5 with the interior portion of the downstream collar portion 3. Cavity 16, as is well-known in the art, creates air flow distortion and perturbations within the gas flow duct thereby increasing aerodynamic losses and degrading engine performance in the forward thrust operating mode.
Typical pivoting door thrust reversing systems for a turbojet engine are described in U.S. Pat. Nos. 4,410,152 and 4,485,970, as well as French Patent 2,559,838. Solutions for improving the air flow through the cold flow air duct in the forward thrust operating mode are also known in the art, a typical example of which may be found in U.S. Pat. No. 4,916,895. This patent describes a thrust reverser door having a movable internal door panel segment which is movable such that it matches the ideal flow surface when the door is in the forward thrust position.
Another problem encountered by known turbojet engine thrust reversers is the controlling of the direction of the gases passing through the opening in the engine housing. This is of particular importance where the turbojet engine is mounted close to the aircraft structure where it would prove detrimental to have the thrust reversing gases contact the adjacent aircraft structure. Such control is also important to prevent the reingestion of the thrust reversing gases by the engine. The thrust reverser in French Patent 2,559,838 provides one attempt at a solution to controlling the shape and direction of the thrust reversing gases by providing a particular orientation to the upstream edge of the thrust reverser opening and/or the shaping of the distal edge of door gas deflector. The technique for controlling the lateral and forward deflections of the thrust reversing gases is defined as "fluid-sheet control".
Other problems have been encountered, especially in instances wherein the turbojet engine is attached to the aircraft such that it extends close to the ground surface. In this instance, as illustrated in FIG. 3 wherein the turbojet engine has four thrust reverser doors, the gases from the lower thrust reversers contact the ground surface at the large angle of incidence. As illustrated in FIG. 3, the turbojet engine 17 is attached beneath aircraft wing 18. When the thrust reverser doors are in their open, reverser thrust positions, they direct gases in flows 15a, 15b, 15c and 15d, respectively. As can be seen, the reverse thrust gas flows 15c and 15d impinge on the ground surface S at a substantially large angle of incidence i.